Un-unmountable /coda

My venus got sick. So I decided to bounce it. So I did a
/etc/init.d/venus.init stop
but after this ran, venus was still alive. So I kill -9'd it.
But I *still* can't umount /coda! There are no processes, as far
as I can see, that are accessing the filesys. No codacon. Nothing.
But umount still refuses to unmount the filesys. Has anyone ever
seen this lossage?
-Olin
# mount | grep coda
coda on /coda type coda (rw)
# ls /coda
ls: /coda: Input/output error
# umount /coda
umount: /coda: device is busy
umount: /coda: device is busy
# ps auxwwg|grep venus
# ps auxwwg|grep coda
#